KR20130042559A - Magnetic field sensor with improved differentiation between a sensed magnetic field signal and a noise signal - Google Patents

Abstract

The magnetic field sensor includes a Hall element that generates a Hall element output signal comprising a magnetic field signal component and an offset signal component in response to the magnetic field. The magnetic field sensor also includes a Hall element modulation circuit that receives the Hall element output signal and generates a modulator circuit output signal. At this time, the Hall element modulation circuit is modulated with a modulation signal having a variable modulation frequency that varies between the minimum and maximum frequencies.

Description

MAGNETIC FIELD SENSOR WITH IMPROVED DIFFERENTIATION BETWEEN A SENSED MAGNETIC FIELD SIGNAL AND A NOISE SIGNAL}

The present invention relates to magnetic field sensor devices. More particularly, it relates to magnetic field sensors that reduce the effects of noise.

Magnetic field sensors for detecting magnetic fields are known. In a magnetic field sensor, the magnetic field is detected by a magnetic field detection element, such as a Hall element or a magnetoresistance element. This magnetic field detection element provides a signal proportional to the detected magnetic field (ie magnetic field signal). In some ways, the magnetic field signal can be an electrical signal.

Magnetic field sensors are used in a variety of applications. Such magnetic field sensors include linear magnetic field sensors for detecting magnetic field density of magnetic fields, current sensors for detecting magnetic fields generated by currents flowing in current carrying conductors, magnetic switches for detecting proximity of ferromagnetic objects, And a rotation detector that detects the passing of the ferromagnetic objects, but is not limited thereto.

In a linear magnetic field sensor, the output signal varies directly with the detected magnetic field. In a magnetic switch, the output signal changes state in response to the detected magnetic field.

Magnetic field sensors are susceptible to noise that tends to degrade the accuracy of magnetic field sensors. Noise can result from various noise sources. Such noise may include, but is not limited to, sources of external magnetic noise fields and sources of external electric noise fields.

It would be desirable to implement a magnetic field sensor that can distinguish noise from the desired magnetic field signal.

One object of the present invention is to provide a magnetic field sensor capable of distinguishing (dividing) noise from a desired magnetic field signal.

The present invention provides a magnetic field sensor having modulated clock signals whose frequency changes over time. These magnetic field sensors produce a magnetic field sensor output signal that provides the ability to more accurately distinguish noise signals from magnetic field signals.

The magnetic field sensor according to embodiments of the present invention may include a Hall element that generates a Hall element output signal including a magnetic field signal component and an offset signal component in response to the magnetic field. In addition, the magnetic field sensor may include a Hall element modulation circuit for receiving the Hall element output signal to generate a modulation circuit output signal. In this case, the Hall element modulation circuit may modulate the magnetic field signal component or the offset signal component with a modulation signal having a variable modulation frequency that varies between a minimum frequency and a maximum frequency.

The magnetic field sensor may also have one or more of the features described below.

According to some embodiments, the first variable modulation frequency may vary in the form of a linear sweep from the first minimum frequency to the first maximum frequency.

According to some embodiments, the first variable modulation frequency may vary in a nonlinear sweep form from the first minimum frequency to the first maximum frequency.

According to some embodiments, the first variable modulation frequency may vary in the form of a plurality of discrete frequency steps from the first minimum frequency to the first maximum frequency.

According to some embodiments, the first variable modulation frequency may vary in the form of a plurality of discrete frequency steps.

According to some embodiments, the magnetic field sensor may further include an amplifier circuit for receiving the modulation circuit output signal and generating an amplifier circuit output signal.

In some embodiments, the amplifier circuit comprises a switching circuit that modulates a signal representing the modulator circuit output signal into a second modulated signal having a second variable modulation frequency that varies between a second minimum frequency and a second maximum frequency. It may include.

According to some embodiments, the second variable modulation frequency may be equal to the first variable modulation frequency, and the second variable modulation frequency may be synchronous to the first variable modulation frequency.

According to some embodiments, the second variable modulation frequency may be different from the first variable modulation frequency, and the second variable modulation frequency may be synchronized with the first variable modulation frequency.

According to some embodiments, the amplifier circuit outputs the modulator circuit output signal at a rate corresponding to a second modulated signal having a second variable modulation frequency that varies between a second minimum frequency and a second maximum frequency. And a sample-hold circuit for sampling a signal representing a.

According to some embodiments, the second variable modulation frequency may be equal to the first variable modulation frequency, and the second variable modulation frequency may be synchronized with the first variable modulation frequency.

According to some embodiments, the magnetic field sensor may further include a filter circuit that receives the amplifier circuit output signal and generates a magnetic field sensor output signal. At this time, the filter circuit is connected to an anti-alias filter for generating an anti-aliased signal, and the anti-alias filter, and the variation associated with the first variation modulation frequency. And a discrete time selective filter for sampling the signal representing the anti-aliased signal according to a sampling signal having a sampling frequency. In addition, the discrete time selection filter may have a changing notch frequency associated with the first varying modulation frequency.

According to some embodiments, the anti-alias filter may have a corner frequency selected to reduce frequency components at least half of the maximum sampling frequency associated with the variable sampling frequency.

According to some embodiments, the variable sampling frequency may be equal to integer times of the first variable modulation frequency.

In some embodiments, the variable sampling frequency can be equal to the first variable modulation frequency.

According to some embodiments, the variable sampling frequency may be equal to twice the first variable modulation frequency.

In some embodiments, the variable notch frequency can be equal to the first variable modulation frequency.

According to some embodiments, the magnetic field sensor may further include a voltage controlled oscillator for generating a voltage controlled oscillator output signal having a variation frequency associated with the first variation modulation frequency.

In example embodiments, the magnetic field sensor may include a clock generation circuit configured to receive the voltage controlled oscillator output signal to generate at least one of the first modulated signal, the second modulated signal, or the sampling signal. It may further include.

According to some embodiments, the magnetic field sensor may further include a signal generation circuit for generating an output signal to control the variable frequency of the voltage controlled oscillator output signal.

According to some embodiments, the output signal of the signal generation circuit may comprise a linear voltage signal that linearly-ramps from a minimum voltage value to a maximum voltage value.

According to some embodiments, the output signal of the signal generation circuit may include a nonlinear voltage signal that varies from a minimum voltage value to a maximum voltage value.

According to some embodiments, the output signal of the signal generation circuit may include a stepped voltage signal that varies in the form of a plurality of discrete voltage steps from a minimum voltage value to a maximum voltage value.

According to some embodiments, the output signal of the signal generation circuit may include a step voltage signal that varies in the form of a plurality of discrete voltage steps.

According to some embodiments, the magnetic field sensor may further include a voltage controlled oscillator for generating a voltage controlled oscillator output signal having a variation frequency associated with the first variation modulation frequency.

The present invention as well as the above-described features of the present invention will be more fully understood from the following detailed description.
1 includes a Hall element, a modulation circuit, an amplifier circuit with a chopper-stabilized amplifier, an anti-alias filter and a filter circuit with a discrete-time selection filter. Is a block diagram representing a conventional magnetic field sensor, where clocked portions are clocked at fixed clocks (ie, clock signals with fixed frequencies).
1A shows another conventional magnetic field sensor having a Hall element, a modulation circuit, an amplifier circuit with a sample-hold circuit, and a filter circuit with a low pass filter, where the clocked portions are at fixed clocks. Clocked).
FIG. 2 is a block illustrating a switched hall element having a Hall element and a modulation circuit that can be used as a modulation element and a Hall element in the magnetic field sensor of FIGS. 1 and 1A to modulate the offset component to a higher frequency. It is also.
FIG. 2A is a graph illustrating clock signals for the switch hall element of FIG. 2. FIG.
FIG. 2B is a graph illustrating the modulation offset component provided by the switch hall element of FIG. 2.
FIG. 2C is a graph illustrating an un-modulated magnetic field signal component provided by the switch hall element of FIG. 2.
FIG. 3 is a block diagram illustrating a Hall element in the magnetic field sensor of FIGS. 1 and 1A and a switch Hall element having a modulation circuit and a Hall element that may be used as a modulation circuit to modulate the magnetic field signal component to a higher frequency.
3A is a graph illustrating clock signals for the switch hall element of FIG. 3.
FIG. 3B is a graph illustrating the unmodulated offset component provided by the switch hole element of FIG. 3.
3C is a graph illustrating a modulated magnetic field signal component provided by the switching hall element of FIG. 3.
4 is a graph showing four signals that are single-ended signals appearing at point A of FIGS. 1 and 1A.
FIG. 4A is a graph illustrating a differential signal having an unmodulated signal component and a modulation offset component appearing at point B in FIG. 1.
FIG. 4B is a graph showing a differential signal having a modulation offset component and a demodulated magnetic field signal component at point C of FIG. 1.
4C is a graph illustrating a filtered differential signal having a filtered modulation offset component and a demodulation signal component appearing at point D in FIGS. 1 and 1A.
5 is a magnetic field sensor having a Hall element, a modulation circuit, an amplifier circuit with a chopper stabilizing amplifier and a filter circuit with an anti-alias filter and a discrete time selection filter, wherein the clocked portions are modulated clock signals. is clocked with clocks whose frequency varies in proportion to signal).
5A shows another magnetic field sensor having a Hall element, a modulation circuit, an amplifier circuit with a sample-hold circuit, and a filter circuit with a low pass filter, where the clocked portions are clocks whose frequency varies in proportion to the modulated clock signal. Clocked).
FIG. 6 is a graph showing a voltage ramp that may be provided as a control signal to the voltage controlled oscillator VCO of FIG. 5 or 5A.
FIG. 6A is a frequency domain graph showing a varying frequency that may be generated as the modulated clock signal of FIG. 5 or 5A in response to the voltage ramp of FIG. 6.
7 shows a modulated signal (where the modulated signal has a varying frequency and its harmonics that may be generated after the first switching circuit inside the amplifier circuit of FIG. 5 or at the output of the modulation circuit of FIG. 5A) and baseband. is a frequency domain graph representing a baseband signal, where the baseband (i.e., demodulated) signal may be generated at the output of the amplifier circuit of FIG. 5 or 5A or at the output of the filter circuit of FIG. 5 or 5A). .
FIG. 8 shows a modulated signal (where the modulated signal can be generated after the first switching circuit inside the amplifier circuit of FIG. 5 or at the output of the modulation circuit of FIG. 5A (but its harmonics are omitted) ), A noise signal (where the noise signal can occur within a band of the modulated signal), a baseband signal (where the baseband signal (ie, demodulated) is the amplifier of FIG. 5 or 5A) May be generated at the output of the circuit or at the output of the filter circuit of FIGS. 5 or 5A, and the noise signal demodulated to the baseband, where the noise signal demodulated to the baseband is output from the amplifier circuit of FIG. 5 or 5A. Or at the output of the filter circuit of FIG. 5 or FIG. 5A).
9 is a time domain graph showing the example modulated clock signal of FIGS. 5 and 5A with a linearly varying frequency.
FIG. 9A is a time domain graph illustrating an output signal that may be generated at point C of FIG. 5 in response to a modulated clock signal having the linear change frequency of FIG. 9 in the presence of a noise signal.
FIG. 9B is a time domain graph illustrating an output signal that may be generated at the output of the filter circuits of FIGS. 5 and 5A in response to a modulated clock signal having the linear change frequency of FIG. 9 in the presence of a noise signal.
10 is a time domain graph illustrating the example modulated clock signal of FIGS. 5 and 5A with frequency steps.
FIG. 10A is a time domain graph illustrating an output signal that may be generated at point C of FIG. 5 in response to a modulated clock signal having the discrete frequency steps of FIG. 10 in the presence of a noise signal.
FIG. 10B is a time domain graph illustrating an output signal that may be generated at the output of the filter circuits of FIGS. 5 and 5A in response to a modulated clock signal having the discrete frequency steps of FIG. 10 in the presence of a noise signal.

Some introductory concepts and terminology are described before describing the invention. As used herein, a "magnetic field sensing element" can be used to describe various types of electronic elements capable of detecting a magnetic field. The magnetic field detection elements may be, but are not limited to, Hall elements, magnetoresistance elements, or magnetotransistors. As is known, there are other types of Hall elements (eg planar Hall elements, vertical Hall elements, and circular Hall elements). As is also known, other types of magnetoresistive elements (eg, anisotropic magnetoresistance (AMR) elements, giant magnetoresistance (GMR) elements, tunneling magnetoresistance; TMR) elements, Indium antimonide (InSb) elements, and magnetic tunnel junction (MTJ) elements).

In this specification, Hall effect elements can be used as examples.

As is known, some of the magnetic field detection elements described above tend to have an axis of maximum sensitivity parallel to the substrate supporting the magnetic field detection element, and others of the magnetic field detection elements described above. Others tend to have a maximum sensitivity axis perpendicular to the substrate supporting the magnetic field detection element. Specifically, most but not all types of magnetoresistive elements tend to have maximum sensitivity axes parallel to the substrate, and most but not all types of hall elements tend to have sensitivity axes perpendicular to the substrate.

As used herein, the term “magnetic field sensor” can be used to describe a circuit that includes a magnetic field detection element. As mentioned above, magnetic field sensors are used in a variety of applications. Such magnetic field sensors include linear magnetic field sensors for detecting magnetic field density of magnetic fields, current sensors for detecting magnetic fields generated by currents flowing in current carrying conductors, magnetic switches for detecting proximity of ferromagnetic objects, And a rotation detector that detects the passing of the ferromagnetic objects, but is not limited thereto.

The circuits and techniques described herein may be suitable for all of the above identified types of magnetic field sensors using Hall effect elements. However, for the sake of simplicity, only examples showing linear magnetic field sensors for detecting the magnetic field density of the magnetic field are described herein.

Referring to FIG. 1, a conventional magnetic field sensor 10 is of the type described in US Pat. No. 7,425,821, registered September 16, 2008, and assigned to the assignee of the present invention, which is incorporated herein by reference in its entirety. The magnetic field sensor 10 comprises a Hall element providing four couplings associated with the modulation circuit 14 and the signals 12a,..., 12d. The signals 12a, ..., 12d may be appropriately selected in pairs by the modulation circuit 14 to form a differential output signal, referred to herein as a magnetic field signal. As will be discussed below, the magnetic field signal has at least two components (ie, a magnetic field signal component responsive to the magnetic field and an offset component that generally does not respond to the magnetic field (typically responding at DC).

Modulation circuit 14 may be of the type described below in more detail in conjunction with FIGS. 2-2C or 3-3C. Preferably, the modulation circuit 14 may be of the type described below in conjunction with FIGS. 2-2C for embodiments in which the first switching circuit 20 is present, and embodiments in which the first switching circuit 20 is not used. It may be of the type described below in conjunction with Figures 3 to 3c for this purpose.

The modulation circuit 14 provides the differential output signals 14a, 14b to an amplifier circuit 16 having a chopper-stabilized amplifier which will be discussed in more detail below. The amplifier circuit 16 also provides differential amplified signals 24a and 24b to the filter circuit 26 which will be described in more detail below. The filter circuit 26 may include a low pass filter 28 that precedes the discrete time (time sampling) select filter. Filter circuit 26 may provide differential output signals 30a, 30b. In some alternative ways, the differential signals 24a, 24b, 30a, 30b may replace single-ended signals.

The differential output signals 30a, 30b may be linear output signals having a value proportional to the magnetic field detected by the hall element 12. In other ways, a comparator (not shown) can receive differential output signals 30a, 30b, in which case the output signal generated by the comparator may be a nonlinear signal with two states. have. At this time, the two states representing the magnetic field signal detected by the hall element 12 may be above or below the threshold.

The amplifier circuit 16 may include a summing node 18 that receives the differential signals 14a and 14b and the differential feedback signals 36a and 36b. Summing node 18 may generate differential signals 18a and 18b. The first switching circuit 20 can receive the differential signals 18a and 18b and can generate the first differential switch signals 20a and 20b. The differential amplifier 22 may receive the first differential switch signals 20a and 20b and generate the differential amplified signals 22a and 22b. The second switching circuit 24 can receive the differential amplification signals 22a and 22b and can generate the second differential switch signals 24a and 24b. The summing node 18, the first switching circuit 20, the differential amplifier 22, and the second switching circuit 24 may constitute a chopper stabilizing amplifier. In some ways, the summing node 18 may be omitted and the differential feedback signals 36a and 36b may not be used.

In addition, the magnetic field sensor 10 receives a clock signal 34a from an oscillator 34 and converts the clock signals 32a, 32b, and 32c into a modulation circuit 14, an amplifier circuit 16, and a filter circuit. And a clock generation circuit 32 that provides each to 26. Therefore, in preferred embodiments, the switching function of the modulation circuit 14, the switching function of the amplifier circuit 16 and the switching function of the filter circuit 26 can be synchronous.

Φ 및 NΦ=

Φ일 수 있다. 클럭 신호들(32a, 32b, 32c)은 정적인 주파수(static frequency)를 가질 수 있다.The modulation circuit 14 may be clocked with a clock signal 32a having a frequency Φ. The first and second switching circuits 20 and 24 may be clocked with a clock signal 32b having a frequency KΦ (where K is an integer multiple of 1/2). The discrete time selection filter 30 may be clocked into a clock signal 32c having a frequency NΦ (where N is an integer). In some ways, KΦ =

Φ and NΦ =

Can be Φ. The clock signals 32a, 32b, and 32c may have a static frequency.

As described above, the differential output signal (i.e., the differential signal is suitably selected in pairs among the signals 12a, ..., 12d) by the modulation circuit 14 is a desired magnetic field that is proportional to the detected magnetic field. It can include both signal components and undesired offset signal components (ie, DC). Although the Hall element 12 generates a signal having both a magnetic field signal component and an offset component (i.e., a differential signal suitably selected in pairs among the signals 12a, ..., 12d) by the modulation circuit 14, It will be apparent from the following description of FIGS. 2-3 that the output signals 30a, 30b from the magnetic field sensor 10 have a predominant magnetic field signal component and a relatively reduced offset component.

While the magnetic field signal component is left in the baseband, the modulation circuit 14 is suitably selected in pairs among the signals 12a, ..., 12d by the Hall element differential signal (i.e. by the modulation circuit 14). It will be understood from the description below for FIGS. 2-2C to modulate (ie, frequency shift) the offset component of the differential signal) to a higher frequency. Thus, the magnetic field signal component and offset component may be separated on frequency after operation of the modulation circuit 14.

In operation, the amplifier circuit 16 with the chopper stabilized amplifier can modulate (to the first switching circuit 20) and demodulate (ie to frequency shift) the baseband and It is possible to create a magnetic field signal component that remains at (e.g., DC or relatively low frequency). In addition, the amplifier circuit can demodulate (with the first switching circuit 20) and re-modulate (ie, frequency shift) with (with the second switching circuit 24) an offset that remains at a higher frequency. You can create components. Thus, the magnetic field signal component and offset component may remain separated on frequency after operation of the amplifier circuit 16.

The filter circuit 26 may reduce the magnitude of the offset component appearing at higher frequencies. Thus, differential output signals 30a and 30b may include magnetic field signal components in the baseband (ie, DC or relatively low frequency) and greatly reduced offset components previously shifted to higher frequencies. .

Further description of the magnetic field sensor 10 can be found in the above-mentioned US Pat. No. 7,425,821.

1A, elements such as those of FIG. 1 are designated by the same reference numerals. Another conventional magnetic field sensor 40 may be of the type described in US Pat. No. 5,621,319, filed April 15, 1997. This US patent is assigned to the assignee of the present invention and is hereby incorporated by reference in its entirety. The magnetic field sensor 40 may include a hall element 12 providing four connections associated with the modulation circuit 15 and the signals 12a,..., 12d. Modulation circuit 15 may be of the type described below in more detail in conjunction with FIGS.

Modulation circuit 15 may provide differential output signals 15a, 15b to amplifying circuit 41 having two sample and hold circuits 43, 44, which will be described in more detail below. The amplifying circuit 41 may provide the differential amplifying signals 46a and 46b to the filter circuit 48 which will be described later in more detail. The filter circuit 48 may provide differential output signals 47a and 47b. In some alternative ways, the differential signals 46a, 46b, 47a, 47b may be single ended signals.

The amplifying circuit 41 may include a differential amplifier 42 which receives the differential signals 15a and 15b and generates the differential amplifying signals 42a and 42b. The first sample-hold circuit 43 may receive the signal 42a as a single-ended signal. The second sample-hold circuit 44 can receive the signal 42b as a single-ended signal. The sample-hold circuit 43 may generate a signal 43a, and the sample-hold circuit 44 may generate a signal 44a. Summing node 45 may receive signals 43a and 44a and may generate a subtracted signal 45a. Amplifier 46 may receive subtracted signal 45a and generate differential signals 46a and 46b.

The filter circuit 48 may include a low pass filter 47 that receives the differential signals 46a and 46b and generates differential filtered signals 47a and 47b.

The magnetic field sensor 40 also receives a clock signal 34a from the oscillator 34 and provides a clock generation circuit for providing the clock signal 49a to the modulation circuit 12 and the amplifier circuit 41. And (49). In preferred embodiments, the switching function of the modulation circuit 15 may be synchronized with the switching function of the amplifier circuit 41.

The modulation circuit 15 can be clocked with a clock signal 49a having a frequency Φ. In addition, the first and second sample-hold circuits 43 and 44 may be clocked with a clock signal 49a. Clock signal 49a has a static frequency. In some embodiments, filter circuit 48 may not be clocked. In other embodiments, filter circuit 48 may include a discrete time selection filter. In this case, the discrete time selection filter may be the same as or similar to the discrete time selection filter 30 of FIG. 1.

As described above, the output signal from the Hall element 12 (i.e., the differential signal suitably selected in pairs among the signals 12a, ..., 12d by the modulation circuit 15) is proportional to the detected magnetic field. It will be understood that it includes both the magnetic field signal component and the offset signal component. Although the Hall element 12 generates a signal having a magnetic field signal component and an offset component (i.e., a differential signal suitably selected in pairs among the signals 12a, ..., 12d) by the modulation circuit 15, the magnetic field It will be apparent from the following description of FIGS. 3 to 3 c that the output signals 47a and 47b from the sensor 40 have a dominant magnetic field signal component and a greatly reduced offset component.

Further, as described above, while the offset component is left in the baseband (e.g., DC), the modulation circuit 15 causes the signals 12a,. It will be understood from the description of FIGS. 3 to 3A to modulate (ie, frequency shift) the magnetic field signal components of a differential signal, suitably selected in pairs from. Thus, the magnetic field signal component and offset component can be separated on frequency by the operation of the modulation circuit 15.

The amplifier circuit 41 with the two sample-hold circuits 43, 44 can demodulate (i.e., frequency shift) the magnetic field signal component returning to the baseband (e.g., DC or low frequency), The offset component can be modulated (ie, frequency shifted) to a higher frequency. Thus, the magnetic field signal component and offset component may remain separated on frequency after operation of the amplifier circuit 41. In addition, the two sample-hold circuits 43, 44 may provide filtering of the resulting signal similar to that provided by the discrete time selection filter 30 of FIG. 1. Therefore, the discrete time selection filter 30 may not be needed in the magnetic field sensor 40.

The filter circuit 48 may include a low pass circuit 47. In operation, filter circuit 48 may further reduce the magnitude of the offset component appearing at higher frequencies. In addition, the filter circuit 48 may reduce any second order components due to the sampling operation. Thus, differential output signals 47a and 47b may include magnetic field signal components in the baseband (eg, DC or low frequency) and greatly reduced offset components previously shifted to higher frequencies.

+로 표시)를 제공할 수 있고, 스위치들(56a, 56d)의 제 2 단자들은 스위치 홀 출력 신호의 음의 노드(negative node)(여기서,

-로 표시)를 제공할 수 있다.Referring to FIG. 2, a switch hall element 50 of the type that modulates a hole offset component may include a hall element 52 (or Hall plate) and a modulation circuit 54. The modulation circuit 54 may be similar or identical to the modulation circuit 14 of FIG. 1. Hall element 52 may include four contacts 52a, 52b, 52c, 52d, and as shown, each of the four contacts 52a, 52b, 52c, 52d may be a switch ( It may be connected to the first terminal (56) of the 56a, 56b, 56c, 56d, respectively. The second terminals of the switches 56b and 56c are positive nodes of the switched hall output signal, where

And the second terminals of the switches 56a and 56d are negative nodes (here,

(Indicated by-).

, ground)에 선택적으로 연결하기 위하여 배치될 수 있다. 보다 상세하게는, 스위치들(56b, 56d, 60a, 60c)은 클럭 신호(CLK)에 의해 제어될 수 있고, 스위치들(56a, 56c, 60b, 60d)은 상보적인 클럭 신호(complementary clock signal)(CLK/)에 의해 제어될 수 있다. 클럭 신호들(CLK, CLK/)은 도 2a에 도시된 바와 같이, 두 가지 상태들 또는 위상들(즉,

상태 및

상태)을 가질 수 있다.Additional switches 60a, 60b, 60c, 60d provide Hall contacts with supply voltage (

can be arranged to connect to the ground, selectively). More specifically, the switches 56b, 56d, 60a, 60c may be controlled by a clock signal CLK, and the switches 56a, 56c, 60b, 60d may be complementary clock signals. Can be controlled by (CLK /). The clock signals CLK, CLK / are in two states or phases (i.e., as shown in FIG. 2A).

Status and

State).

)에서, 전류는 단자(52a)에서부터 단자(52c)까지 흐르고, 스위치 홀 출력 신호(

)는

(단,

는 홀 요소 오프셋 전압 또는 홀 오프셋 컴포넌트이고,

는 자기장 신호 컴포넌트임)와 같다. 위상(

)에서, 전류는 단자(52b)부터 단자(52d)까지 흐르고, 스위치 홀 출력 신호(

)는

와 같다. 따라서, 변조 회로(54)는 홀 오프셋 컴포넌트(

)를 변조한다. 이 때, 도 2b에는 0이 아닌 자기장인 경우가 도시되어 있다. 자기장 신호 컴포넌트(

)는 도 2c에서 도시된 바와 같이, 실질적으로 불변 상태(invariant)로 남는다. In operation, the phase (

), Current flows from terminal 52a to terminal 52c, and the switch hole output signal (

)

(only,

Is a Hall element offset voltage or Hall offset component,

Is a magnetic field signal component). Phase(

), Current flows from terminal 52b to terminal 52d, and the switch hole output signal (

)

Same as Thus, the modulation circuit 54 is a hole offset component (

Modulate In this case, FIG. 2B illustrates a case where the magnetic field is not zero. Magnetic field signal component

) Remains substantially invariant, as shown in FIG. 2C.

+로 표시)를 제공할 수 있다. 스위치들(56c, 56d)의 제 2 단자들은 스위치 홀 출력 신호의 음의 노드(여기서,

-로 표시)를 제공할 수 있다. 따라서, 도 2 및 도 3의 비교는 위상(

)에서 홀 요소의 출력 접합들이 교환된다는(interchanged) 것을 보여주고 있다.Referring to FIG. 3, an alternate switched Hall element 70 of the type that modulates a magnetic signal component may include a hall element 72 and a modulation circuit 74, and a modulation circuit 74. May be the same as or similar to the modulation circuit 15 of FIG. 1A. Hall element 72 may be identical to hall element 52 of FIG. 2 and may include four junctions 72a, 72b, 72c, 72d. In this case, each of the four junctions 72a, 72b, 72c, and 72d may be connected to the first terminal of each switch 76a, 76b, 76c, or 76d, respectively. The second terminals of the switches 76a, 76b are positive nodes of the switch hall output signal, where

(Marked with +). The second terminals of the switches 56c and 56d are negative nodes of the switch hall output signal, where

(Indicated by-). Thus, the comparison of FIGS.

Shows that the output junctions of the Hall elements are interchanged.

, ground)에 선택적으로 연결하기 위하여 배치될 수 있다. 스위치들(76b, 76d, 80a, 80c)은 클럭 신호(CLK)에 의해 제어될 수 있고, 스위치들(76a, 76c, 80b, 80d)은 상보적인 클럭 신호(CLK/)에 의해 제어될 수 있다. 도시된 바와 같이, 클럭 신호들(CLK, CLK/)은 도 2의 신호들과 동일할 수 있고, 그에 따라 두 가지 상태들 또는 위상들(

,

)을 가질 수 있다.The additional switches 80a, 80b, 80c, 80d connect the hole junctions 72a, 72b, 72c, 72d to the supply voltage (

can be arranged to connect to the ground, selectively). The switches 76b, 76d, 80a, 80c may be controlled by the clock signal CLK, and the switches 76a, 76c, 80b, 80d may be controlled by the complementary clock signal CLK /. . As shown, the clock signals CLK, CLK / may be the same as the signals of FIG. 2, thus providing two states or phases (

,

)

)에서, 전류는 단자(72a)에서부터 단자(72c)까지 흐르고, 스위치 홀 출력 신호(

)는

와 동일하다. 위상(

)에서, 전류는 단자(72b)에서부터 단자(72d)까지 흐르고, 스위치 홀 출력 신호(

)는

와 동일하다. 따라서, 변조 회로(74)는 자기 신호 컴포넌트를 변조하여 변조 자기 신호 컴포넌트(

)를 제공할 수 있다. 이 때, 도 3c에는 0이 아닌 자기장의 경우가 도시되어 있다. 오프셋 컴포넌트(

)는 도 3b에서 도시된 바와 같이 실질적으로 불변 상태로 남는다.In operation, the phase (

), Current flows from terminal 72a to terminal 72c, and the switch hole output signal (

)

. Phase(

), Current flows from terminal 72b to terminal 72d, and the switch hole output signal (

)

. Thus, the modulation circuit 74 modulates the magnetic signal component to modulate the magnetic signal component (

) Can be provided. In this case, the case of the non-zero magnetic field is shown in FIG. Offset component (

) Remains substantially unchanged as shown in FIG. 3B.

In a preferred embodiment, the modulation circuit 14 of FIG. 5 is of the type described in conjunction with FIGS. 2-2C, and the modulation circuit 15 of FIG. 5A is of the type described in conjunction with FIGS. 3-3C. It will be understood from the description below for 5 to 5a. In other words, in a preferred embodiment, the amplifier circuit 16 of FIG. 5 may receive differential signals 14a, 14b having a modulation offset component and an un-modulated magnetic field signal component. Conversely, in a preferred embodiment, the amplifier circuit 41 of FIG. 5A can receive differential signals 15a, 15b having a modulated magnetic field signal component and a non-modulated offset component.

4 through 4C, graphs 100, 120, 140, and 160 illustrate signals appearing at points A, B, C, and D of FIG. 1. Each of these graphs 100, 120, 140, 160 has a horizontal axis, which is a unit of time, and a vertical axis, which is a unit of voltage.

In the manner of FIG. 1A, the signals A ′, B ′, D ′ of FIG. 1A may be similar to the signals A, B, D of FIGS. 1 and 4-4C. The operation of magnetic field sensor 40 of FIG.

)와 도 2의 신호(CLK)의 어떠한 반주기(half cycle)에서, 신호들(102, 108 또는 104, 106) 중에서 2개가 도 2의 신호들(

+,

-)로서 변조 회로의 출력에서 나타날 수 있다. 이 때, 도 2의 신호들(

+,

-)은 도 1의 차동 신호(14a, 14b)(즉, 도 1의 신호(B))일 수 있다. 도 2의 신호들(

+,

-) 사이의 차이와 도 1의 신호들(14a, 14b) 사이의 차이는 차동 신호들이다.The graph 100 may include four signals 102, 104, 106, 108, and as shown in FIG. 1, each of the four signals 102, 104, 106, 108 may represent signals ( 12a, 12b, 12c, and 12d, respectively (ie, the signal A). Also, each of the four signals 102, 104, 106, 108 represents four signals received by the switches 56a, 56b, 56c, 56d of FIG. 2. The clock signal of FIG.

) And at any half cycle of the signal CLK of FIG. 2, two of the signals 102, 108 or 104, 106 are the signals of FIG.

+,

May appear at the output of the modulation circuit. At this time, the signals of FIG.

+,

−) May be the differential signals 14a and 14b of FIG. 1 (ie, signal B of FIG. 1). Signals of FIG.

+,

The difference between-) and the difference between the signals 14a and 14b of FIG. 1 are differential signals.

,

)의 합(sum)을 나타내며, 도 1의 차동 신호(B)를 나타낸다. 신호(122)의 AC 부분은 신호(122)의 변조 오프셋 컴포넌트를 나타낸다. 라인(line)(124)은 신호(122)(즉, 변조되지 않는 자기장 신호 컴포넌트인 신호(122)의 자기장 신호 컴포넌트)의 DC 부분(또는 낮은 주파수 부분)을 나타낸다.In phase Ph 0, signals 104 and 106 differ by an amount 110. In phase Ph 90, signals 108 and 102 are different by amount 112 and are opposite in polarity to the difference between signals 104 and 106. The signal 122 of FIG. 4A represents the above-described difference of signals, and the signals of FIGS. 2B and 2C (

,

Sum is shown, and the differential signal B of FIG. The AC portion of the signal 122 represents the modulation offset component of the signal 122. Line 124 represents the DC portion (or low frequency portion) of signal 122 (ie, the magnetic field signal component of signal 122, which is an unmodulated magnetic field signal component).

Signal 144 represents differential signals 28a, 28b of FIG. 1 (ie, signal C of FIG. 1). Signal 144 may have rounded edges due to the band limiting effects of low pass filter 28 of FIG. 1, depending on the frequency of clock signal 32b of FIG. 1. . Signal 144 may be greater than signal 122 by amplification provided by the amplifier circuit 16 of FIG. 1. Signal 144 may have an AC portion representing offset component 124 of FIG. 4A, and may be a modulation offset component generated via amplifier circuit 16 (ie, a chopper stabilized amplifier) of FIG. 1. Line 142 may represent a DC portion of signal 144 and may be a demodulated version of the AC portion of modulated magnetic field signal 122 (ie, the magnetic field signal component).

The desired signal (magnetic field component) is the DC portion (or low frequency portion) of signal 144 (where the DC portion is represented by line 142) and the unwanted signal (offset component) is signal 144. You should know that this is the AC part of. Further, when the magnetic field sensor 10 of FIG. 1 detects a static magnetic field, it will be understood that the DC portion of the signal 144 represented by the line 142 is only a DC signal. In other words, if the magnetic field sensor 10 of FIG. 1 detects a changing magnetic field, the DC portion of the signal 144 represented by line 142 will have a varying (AC) portion.

Curve 164 represents the differential signals 30a, 30b of FIG. 1 (ie, signal D of FIG. 1). Curve 164 may be a filtered version of curve 144. Filtering signal 144 to obtain signal 164 may eliminate much of the AC portion of signal 144 while leaving a signal closer to the desired DC portion (magnetic field signal component) of signal 144. . At this time, lines 142 and 162 represent the desired DC portion of signal 144. However, as described above, when the magnetic field sensor 10 of FIG. 1 detects a static magnetic field, the DC portion of the signal 164 represented by line 162 is only a DC signal.

,

)의 합을 나타내고, 도 1a의 차동 신호(B')를 나타낸다. 신호(122)의 AC 부분은 신호(122)의 변조 자기장 신호 컴포넌트를 나타낸다. 라인(124)은 신호(122)의 DC 부분(또는 저 주파수 부분) 즉, 신호(122)의 오프셋 컴포넌트를 나타낸다. 그러므로, 도 4a를 참조하면, 도 1의 신호(B)와 다른 도 1a의 신호(B')를 위하여 자기장 신호는 변조될 수 있고, 오프셋 컴포넌트는 변조되지 않을 수 있다.It will be appreciated that the signals of FIGS. 4, 4A, and 4C are similar to the signals A ', B', D 'of FIG. 1A. However, in relation to FIG. 1A, the signal 122 of FIG. 4A is divided into the signals of FIGS. 3B and 3C (

,

) And the differential signal B 'of FIG. 1A. The AC portion of signal 122 represents the modulated magnetic field signal component of signal 122. Line 124 represents the DC portion (or low frequency portion) of signal 122, that is, the offset component of signal 122. Therefore, referring to FIG. 4A, the magnetic field signal may be modulated for the signal B ′ of FIG. 1A different from the signal B of FIG. 1, and the offset component may not be modulated.

5, elements such as those of FIG. 1 are designated by the same reference numerals. The magnetic field sensor 200 may be similar to the magnetic field sensor 10 of FIG. 1. However, the magnetic field sensor 200 may include a voltage controlled oscillator (VCO) 218 that receives the VCO control signal 220a generated by the VCO control signal generator 220. The VCO 218 may generate a VCO output signal 218a whose frequency changes in response to the VCO control signal 220a. The clock generation circuit 216 can receive the VCO output signal 218 and can generate clock signals 216a, 216b, 216c of varying frequency.

Similar to the clock generation circuit 32 of FIG. 1, the clock generation circuit 216 provides the clock signals 216a, 216b, and 216c to the modulation circuit 14, the amplifier circuit 16, and the filter circuit 26, respectively. Can provide. Therefore, in the preferred embodiment, the switching function of the modulation circuit 14, the switching function of the amplifier circuit 16 and the switching function of the filter circuit 26 can be synchronized.

)를 갖는 클럭 신호(216a)로 클럭될 수 있다. 제 1 및 제 2 스위칭 회로(20, 24)는 주파수(

)(단,

는 1/2의 정수 배)를 갖는 클럭 신호(216b)로 클럭될 수 있다. 이산 시간 선택 필터(30)는 주파수(

)를 갖는 클럭 신호(216c)로 클럭될 수 있다. 몇몇 방식들에서,

이고,

이다. 그러나, 도 1의 자기장 센서(10)와는 달리, 클럭 신호들(216a, 216b, 216c)은 비정적인(non-static)(즉, 변화하는) 주파수들을 가질 수 있다.Like the magnetic field sensor 10 of FIG. 1, the modulation circuit 14 has a frequency (

Clock signal 216a with The first and second switching circuits 20, 24 have a frequency (

)(only,

May be clocked into a clock signal 216b having an integer multiple of 1/2). Discrete time selection filter 30 has a frequency (

Clock signal 216c). In some ways,

ego,

to be. However, unlike the magnetic field sensor 10 of FIG. 1, the clock signals 216a, 216b, 216c may have non-static (ie, varying) frequencies.

In particular, the clock signal 216a may be a first modulated signal having a first variable modulation frequency that varies between the first minimum frequency and the first maximum frequency. In some embodiments, the first variable modulation frequency may vary from the first minimum frequency to the first maximum frequency in the form of a linear sweep. In some other embodiments, the first variable modulation frequency may vary from the first minimum frequency to the first maximum frequency in the form of a non-linear sweep. In some other embodiments, the first variable modulation frequency may vary from the first minimum frequency to the first maximum frequency in the form of a plurality of discrete frequency steps. In some other embodiments, the first variable modulation frequency can vary in the form of a plurality of discrete frequency steps. In some embodiments, the discrete frequency steps may be steps in the form of a pseudorandom noise pattern.

Similarly, clock signal 216b may be a second modulated signal having a second variable modulation frequency that varies between a second minimum frequency and a second maximum frequency. In some embodiments, the second variable modulation frequency may be the same and synchronized with the first variable modulation frequency of the first clock signal 216a. In some other embodiments, the second variable modulation frequency may be different but synchronized with the first variable modulation frequency of the first clock signal 216a.

Similarly, clock signal 216c may be a sampling signal having a variable sampling frequency associated with a first variable modulation frequency of first clock signal 216a or second clock signal 217b. At this time, the discrete time selection filter 30 may have a variation notch frequency associated with the first variation modulation frequency. In some embodiments, the variable sampling frequency can be equal to integer times of the first variable modulation frequency of the first clock signal. In some embodiments, the variable sampling frequency can be the same as the first variable modulation frequency. In some embodiments, the variable sampling frequency may be equal to twice the first variable modulation frequency. In some embodiments, the variable notch frequency can be the same as the first variable modulation frequency.

In some embodiments, anti-aliasing filter 28 may have a corner frequency selected to reduce frequency components of at least half of the maximum sampling frequency associated with the variable sampling frequency.

Differential signals 204a-204b, 215a-215b, 206a-206b, 207a-207b, 208a-208b, 210a-210b, 212a-212b, 214a-214b are signals 14a-14b, 36a-36b of FIG. , 18a-18b, 20a-20b, 22a-22b, 24a-24b, 28a-28b, 30a-30b, but will generally be different due to the use of other clock signals 216a, ..., 216c. Can be. The differential signal (i.e., the differential signal suitably selected in pairs among the signals 204a, ..., 204d by the modulation circuit 14) is represented by the differential signal (i.e., the modulation circuit 14) of FIG. 12a, ..., 12d) may be the same as or similar to the differential signal appropriately selected in pairs.

5A, elements such as those of FIGS. 1A and 5 are designated by the same reference numerals. The magnetic field sensor 230 is similar to the magnetic field sensor 40 of FIG. 1A. However, the magnetic field sensor 230 may include a voltage controlled oscillator (VCO) 218 that receives the VCO control signal 220a generated by the VCO control signal generator 220. The VCO 218 may generate a VCO output signal 218a whose frequency changes in response to the VCO control signal 220a. The clock generation circuit 217 can receive the VCO output signal 218a and can generate the clock signal 217a.

Similar to the clock generation circuit 49 of FIG. 1A, the clock generation circuit 217 may provide a clock signal 217 to the modulation circuit 15 and the amplifier circuit 41. Therefore, in preferred embodiments, the switching function of the modulation circuit 15 can be synchronized with the switching function of the amplifier circuit 41. In some embodiments, filter circuit 48 may not be clocked. In some embodiments, filter circuit 48 may include a discrete time selection filter. The discrete time selection filter may be the same as or similar to the discrete time selection filter 30 of FIG. 5, in which case another clock signal may be provided to clock the discrete time selection filter.

Similar to clock signal 216a of FIG. 5, clock signal 217a may be a modulated signal having a variable modulation frequency that varies between the minimum and maximum frequencies. In some embodiments, the variable modulation frequency may vary from minimum frequency to maximum frequency in the form of a linear sweep. In some embodiments, the variable modulation frequency may vary from minimum frequency to maximum frequency in the form of a nonlinear sweep. In some other embodiments, the variable modulation frequency may vary from minimum frequency to maximum frequency in the form of a plurality of discrete frequency steps. In some other embodiments, the variable modulation frequency may vary in the form of a plurality of discrete frequency steps. In some embodiments, the discrete frequency steps may be steps in the form of a pseudo random noise pattern.

Signals 205a-205b, 232a-232b, 234a, 235a, 236, 238a-238b, 240a-240b are signals 14a-14b, 42a-42b, 43a, 44a, 45a, 46a-46b, While generally corresponding to 47a-47b, it may be different due to the use of other clock signals 217a. The differential signals 202b and 202c may be similar or identical to the differential signals 12b and 12c of FIG. 1A.

6 to 10 show examples of signals generated during operation of the magnetic field sensor 200 of FIG. 5. It will be understood that similar signals occurring during operation of the magnetic field sensor 230 of FIG. 5A are not explicitly shown.

Referring to FIG. 6, the graph 250 has a horizontal axis that is an arbitrary time unit and a vertical axis that is an arbitrary voltage unit. Curve 252, sweeping from the minimum voltage 254 to the maximum voltage 256, represents one particular embodiment of the VCO control signal 220a of FIG. 5 and of the frequency of the clock signals 216a, 216b, 216c. Corresponds to a linear sweep.

While curve 252 linearly-ramps in the upward direction of time, curve 252 may linearly-change in the downward direction during other time intervals. At this time, the linear-change in the up direction and the down direction can be repeated periodically.

와

사이에서 주파수가 위쪽으로 스위프한 후 아래쪽으로 스위프할 수 있다. 여기서, 주파수(

) 즉, 클럭 신호(216a)의 초핑 주파수(chopping frequency)(변조 주파수)가 스위프 범위(sweep range)의 중심인 중심 주파수(center frequency)일 수 있다. 다른 실시예들에서, 클럭 신호(216a)의 주파수는 주파수가 오직 위쪽 또는 아래쪽으로만 주기적으로 스위프한 후, 다른 극값(extreme value)으로 빠르게 리셋(reset)될 수 있다.Referring to FIG. 6A, the graph 260 has a horizontal axis that is an arbitrary frequency unit and a vertical axis that is an arbitrary power unit. Graph 260 may represent a frequency domain. In the case where the VCO control signal 220a is an upward sweep of the frequency as shown in FIG. 6, the lines 262a,..., 262e are a plurality of instantaneous snaps to the clock signal 216a of FIG. 5. Represents instantaneous snapshots. However, it linearly changes downward (not shown) with a downward sweep of frequency. Arrows 264a and 264b indicating the frequency of the clock signal 216a are the minimum frequencies.

Wow

The frequency can be swept upwards and then swept downwards. Where frequency (

That is, the chopping frequency (modulation frequency) of the clock signal 216a may be a center frequency that is the center of the sweep range. In other embodiments, the frequency of clock signal 216a may be quickly reset to another extreme value after the frequency periodically sweeps only up or down.

Referring to FIG. 7, the graph 300 has a horizontal axis that is an arbitrary frequency unit and a vertical axis that is an arbitrary power unit. The graph 300 may represent a frequency domain. When clock signal 216a is an upward sweep of frequency as shown in FIG. 6A, lines 302a, ..., 302c are the fundamental frequencies of the magnetic field signal components of differential signal 207a, 207b of FIG. Represents a plurality of instantaneous snapshots for (fundamental frequency). However, it linearly changes downward (not shown) with a downward sweep of frequency. The finite width of lines 302a, ..., 302c is such that the magnetic field signal component (i.e., Hall element 12 of FIG. 5) has signal content at DC as well as at relatively low frequencies. Magnetic field detected by Arrows 306a and 306b indicate that the frequencies of the differential signals 207a and 207b can sweep upwards on frequency in a periodic fashion and then sweep downwards.

Lines 304a, ..., 304c may represent a plurality of instantaneous snapshots of the third harmonic of the magnetic field signal component of differential signal 207a, 207b of FIG. The modulation circuit 14 of FIG. 5 (such as the circuit of FIG. 2, for example) multiplies the differential signals 202b and 202c of FIG. 5 by a square wave (clock signal 216a). It will be understood as a circuit. Thus, third-order harmonics (and other odd harmonics) of the sweeping frequency represented by lines 302a, ..., 302c may be generated. Lines 304a,..., 304c may represent third harmonics, and other odd harmonics may be generated by modulation circuit 14.

)는 대략 300Khz일 수 있다.In some embodiments, the center frequency (

) Can be about 300Khz.

과 동일한 파워를 가질 수 있다.Although lines 304a, ..., 304c do not appear to be in proper relative proportions to lines 302a, ..., 302c, the power of lines 302a, ..., 302c does not appear.

It may have the same power as.

A dashed line 307 (narrow spectrum) may represent the magnetic field signal component of the differential signals 210a and 210b (FIG. 5) at the output of the amplifier circuit 16. That is, when clocked by the swept clock signal 216b, after being demodulated back to baseband by the operation of the amplifier circuit 16 (by the second switching circuit 24), the dashed line 307 is shown in FIG. Swept signals 302a, ..., 302c (ie, differential signals 207a, 207b representing magnetic field signal components). This demodulation results in a line (narrowband) spectrum 307. Differential signals 210a and 210b, represented by dashed lines 307, appear at or near DC and are not swept in this embodiment.

Curve 308 may represent a pass band of filter circuit 26.

Referring to FIG. 8, elements such as those of FIG. 7 are designated by the same reference numerals. Graph 320 has a horizontal axis that is an arbitrary frequency unit and a vertical axis that is an arbitrary power unit. Graph 320 may represent a frequency domain. When clock signal 216a is an upward sweep of frequency as shown in FIG. 6A, lines 302a, ..., 302c are the basis of the magnetic field signal component of differential signal 207a, 207b of FIG. Represent a plurality of instantaneous snapshots of frequencies. However, it linearly changes downward (not shown) with a downward sweep of frequency. The third harmonics 304a, ..., 304c of FIG. 7 are not shown.

Line (frequency) 322 represents noise. Such noise may be magnetic field noise, for example, where the line 322 can be detected by the hall element 12 of FIG. 5. Alternatively, such noise may be, for example, electrical noise such that line 322 may be connected to Hall element 12, modulation circuit 14, or amplifying circuit 16 of FIG. 5 before switching circuit 24. (Note: if injected after switching circuit 24, noise is not modulated back to baseband). This typical noise signal 322 is stationary in frequency.

)는 대략 300Khz일 수 있고, 노이즈(322)는 정적이거나 또는 대략 300Khz의 거의 정적인 주파수를 가질 수 있다. 그러나, 도 9b에 대한 아래의 설명으로부터, 도 5의 자기장 센서(200)(및 도 5a의 자기장 센서(230))는 중심 주파수(

)가 아닌 주파수들에서 노이즈 신호들 및 주파수가 변동되지 않는 노이즈 신호들을 위하여 이점(advantage)들을 제공할 수 있다. 그럼에도 불구하고, 도 8에 도시된 예에서는, 명확화를 위하여, 중심 주파수(

)와 동일한 주파수에서의 노이즈 신호(322)가 도시되어 있다.In some ways, the center frequency (

) May be approximately 300Khz and noise 322 may be static or have a nearly static frequency of approximately 300Khz. However, from the following description of FIG. 9B, the magnetic field sensor 200 (and magnetic field sensor 230 of FIG. 5A) of FIG.

Advantages may be provided for noise signals at frequencies other than) and for noise signals that do not vary in frequency. Nevertheless, in the example shown in FIG. 8, for clarity, the center frequency (

A noise signal 322 at the same frequency as is shown.

The group of lines 324 is demodulated by the operation of the amplifier circuit 16 of FIG. 5 (i.e., when the frequency of the clock signals 216a, ..., 216c is swept along FIG. 6A). A spectral line 322 of the differential signal 210a, 210b or 212a, 212b of FIG. 5 is shown.

Since noise (i.e., spectral line 322) does not vary in frequency when it is demodulated to clock signal 216b with sweeping frequency, a group of lines 324 may represent a baseband signal with sweeping frequency. . If the unchanged clock is used for demodulation by the amplifier circuit 16 instead of the swept clock 216b (as shown in FIG. 1), the demodulated noise signal may appear at or near DC, and the desired demodulation signal. (desired demodulated signal) 307 (magnetic field signal component). This combination can reduce the accuracy of the desired demodulated signal 307.

9-9B illustrate the frequency of FIG. 5 when the clock signal 216a has a frequency that varies linearly up and down between the minimum and maximum frequencies (as described above in conjunction with FIGS. 6 and 6A). Typical signals that may appear during operation of the magnetic field sensor 200 are shown. In contrast, FIGS. 10-10B show the magnetic field sensor 200 of FIG. 5 when the clock signal 216a has a frequency that changes up and down between a minimum frequency and a maximum frequency in the form of a plurality of discrete frequency steps. It shows the signals that can appear during the operation of. Although other embodiments have been described above in conjunction with FIG. 5, other typical signals are not explicitly shown herein.

Referring to FIG. 9, the graph 340 has a horizontal axis of several microseconds time units and a vertical axis of hertz (Hz) frequency units. Waveform 342 may represent the frequency of clock signal 216a of FIG. 5. It may linearly change upwards and then, in some embodiments, linearly change downward (not shown). Thus, clocks 216b and 216c can sweep up and down.

Referring to FIG. 9A, graph 360 has a horizontal axis that is a few microseconds time units and a vertical axis that is a few millivolts voltage units. The signal 362 may represent the differential signals 212a and 212b of FIG. 5 when the magnetic field sensor 200 of FIG. 5 generates noise (eg, the noise 322 of FIG. 8 where the frequency is static). . Thus, signal 362 represents a signal that sweeps the frequency represented by the group of lines 324 of FIG. As described above in conjunction with FIG. 8, signal 362 represents a noise signal 322 demodulated by the amplifier circuit 16 (second switching circuit 24) of FIG. 5 to the baseband. However, signal 362 is swept in frequency due to the operation of the swept clock signals 216a, ..., 216c.

In signal 362, the high frequency component may be viewed as riding upon a lower frequency sinusoid. The high frequency component may represent the offset component of the differential signal generated by the Hall element, and the frequency may be shifted to a higher frequency by the operation of the modulation circuit 14 and the amplifier circuit 16 of FIG.

Referring to FIG. 9B, the graph 380 has a horizontal axis of several microsecond time units and a vertical axis of several millivolt voltage units. The signal 382 may represent the differential signals 214a and 214b of FIG. 5 when the magnetic field sensor 200 of FIG. 5 generates noise (eg, the noise 322 of FIG. 8 where the frequency is static). . Signal 382 is similar to signal 362 of FIG. 9A, but passes through discrete time selection filter 30 of FIG. 5. The high frequency component of the signal 362 of FIG. 9A may be removed by operation of the filter circuit 26 of FIG. 5. Sample steps may be seen in signal 382, may be a discrete sampling result of discrete time selection filter 30, and may be removed by an additional filter (not shown) if desired.

Signals 362 and 382 contain noise seen as a frequency sweeping signal, and the desired signal (i.e., the magnetic field signal component of differential signals 202b and 202c generated by Hall element 12) is a differential signal. When the magnetic field signal component of 202b and 202c is DC, it may be the DC portion of signals 362 and 382. This DC portion appears to be zero volts, but may be another value that is proportional to the magnetic field detected by the hall element 12.

If the clock signals 216a, ..., 216c of FIG. 5 have a static frequency like the clock signals 32a, ..., 32c of FIG. 1, the static noise signal 322 of FIG. When demodulated (by the second switching circuit 24 of FIG. 5), the frequency will not be swept according to the group of lines 324 of FIG. 8, but will be at one frequency. The static noise signal 322 of FIG. 8 may approach (slowly change) to or close to DC, thereby inaccurate detection results of the magnetic field signal components of the signals 214a and 214b of FIG. 5. However, since the swept clock signals 216a, ..., 216c produce a noise signal with frequency sweep, the noise signal can be easily identified and eliminated by subsequent processing or subsequent filtering leaving only the desired magnetic field signal component. Can be.

This subsequent process or subsequent filtering may be provided to the processing module 222 shown in FIGS. 5 and 5A, which may be used to generate the differential signals 214a, 214b or 240a, 240b of FIG. 5 or 5A, respectively. Can be received. In some embodiments, processing module 222 may be a simple low pass filter. In other embodiments, processing module 222 may include another discrete time selection filter. In some embodiments, processing module 222 may include a digital filter. In some embodiments, the processing module 222 selects a stable time region of the differential signal 214a, 214b or 240a, 240b, and determines the DC value (or , Logic that calculates slowly changing values).

The differentiation between the noise signal and the magnetic field signal component is dependent on the differential signal (i.e., the modulation circuit 14) whose frequency changes relatively slowly, unless a varying noise signal is present at the frequency of the magnetic field signal component (including DC). Thereby remaining true for the magnetic field signal component of the differential signal suitably selected from among the signals 202a, ..., 202d. In addition, the distinction between a noise signal and a magnetic field signal component may include a differential signal whose frequency changes relatively, i.e., unless the changing frequency of the noise signal is at the frequency of the changing frequency of the magnetic field signal component. , 202d) may remain precisely for the magnetic field signal component of the differential signal appropriately selected in pairs, and the noise signal may vary in frequency.

Referring to FIG. 10, the graph 400 has a horizontal axis that is several microseconds time units and a vertical axis that is hertz (Hz) frequency units. Waveform 402 may represent the frequency of clock signal 216a of FIG. 5, and waveform 402 may take the form of discrete steps up, and in some embodiments, waveform ( 402 may take the form of discrete steps down. Thus, the clocks 216b and 216c can step up and step down in the form of discrete frequency steps.

Referring to FIG. 10A, the graph 420 has a horizontal axis of several microseconds time unit and a vertical axis of several millivolts voltage unit. Signal 422 may represent differential signals 212a and 212b of FIG. 5 when noise is generated in magnetic field sensor 200 of FIG. 5 (eg, noise signal 322 of FIG. 8 in which frequency is static). have. Thus, signal 422 can also represent a signal stepping in frequency, and signal 422 can be represented by a group of lines 324 of FIG. 8. As described above in conjunction with FIG. 8, signal 422 represents the noise signal 322 of FIG. 8 demodulated by the amplifier circuit 16 of FIG. 5 to the baseband, but with frequency stepping clock signals 216a. The frequency steps due to the operation of ..., 216c).

At signal 422, the high frequency component may be seen as riding a lower frequency stepped signal. The component may represent an offset component of the differential signals 202b and 202c generated by the hall element 12, the frequency being higher by the operation of the modulation circuit 14 and the amplifier circuit 16 of FIG. 5. Can be shifted to

Referring to FIG. 10B, the graph 440 has a horizontal axis of several microseconds time unit and a vertical axis of several millivolts voltage unit. The signal 442 may represent the differential signals 214a and 214b of FIG. 5 when the magnetic field sensor 200 of FIG. 5 generates noise (eg, the noise 322 of FIG. 8 where the frequency is static). . Signal 422 may be similar to signal 422 of FIG. 10A, but may pass through discrete time selection filter 30 of FIG. 5. The high frequency component of signal 422 of FIG. 10A may be removed by operation of filter circuit 26 of FIG. 5. Sample steps can be seen in signal 422 and can be removed by an additional filter (not shown) if desired.

The description of FIG. 9B relating to the distinction between noise signal and magnetic field signal components is substantially the same with respect to FIGS. 10-10B. Therefore, the above description will not be repeated here.

As discussed above, other clock signals 216a, ..., 216c may provide other types of modulations. However, they have the same ability to distinguish the magnetic field signal component from the noise signal while substantially removing the offset component.

All citations cited herein are hereby incorporated by reference in their entirety.

In the above, preferred embodiments have been described in order to describe various concepts, structures and techniques corresponding to the contents of the present patent. However, it will be apparent to those skilled in the art that other embodiments incorporating the concepts, structures, and techniques may be used. Therefore, it should be understood that the scope of the present patent should not be limited to the disclosed embodiments, but should be limited by the spirit and scope of the appended claims.

Claims (25)

A Hall element for generating a Hall element output signal comprising a magnetic field signal component and an offset signal component in response to the magnetic field; And
Receiving the Hall element output signal to generate a modulated circuit output signal, the magnetic field signal component or the offset signal component being a first modulated signal having a first varying modulation frequency that varies between a first minimum frequency and a first maximum frequency Magnetic field sensor comprising a Hall element modulation circuit for modulating. 2. The magnetic field sensor of claim 1, wherein the first variable modulation frequency varies in the form of a linear sweep from the first minimum frequency to the first maximum frequency. 2. The magnetic field sensor of claim 1, wherein the first variable modulation frequency varies in a nonlinear sweep form from the first minimum frequency to the first maximum frequency. The magnetic field sensor of claim 1, wherein the first variable modulation frequency varies in the form of a plurality of discrete frequency steps from the first minimum frequency to the first maximum frequency. 2. The magnetic field sensor of claim 1, wherein the first variable modulation frequency varies in the form of a plurality of discrete frequency steps. The method of claim 1,
And an amplifier circuit for receiving the modulator circuit output signal and generating an amplifier circuit output signal. 7. The circuit of claim 6, wherein the amplifier circuit comprises a switching circuit for modulating a signal representing the modulator circuit output signal into a second modulated signal having a second variable modulation frequency that varies between a second minimum frequency and a second maximum frequency. Magnetic field sensor, characterized in that. 8. The magnetic field sensor of claim 7, wherein the second variable modulation frequency is equal to the first variable modulation frequency and the second variable modulation frequency is synchronous with the first variable modulation frequency. 8. The magnetic field sensor of claim 7, wherein the second variable modulation frequency is different from the first variable modulation frequency, and wherein the second variable modulation frequency is synchronized with the first variable modulation frequency. 7. The amplifier circuit of claim 6, wherein the amplifier circuit outputs the modulator circuit output signal at a rate corresponding to a second modulated signal having a second variable modulation frequency that varies between a second minimum frequency and a second maximum frequency. And a sample-hold circuit for sampling the representative signal. The magnetic field sensor of claim 10, wherein the second variable modulation frequency is equal to the first variable modulation frequency, and the second variable modulation frequency is synchronized with the first variable modulation frequency. The method according to claim 6,
And a filter circuit for receiving the amplifier circuit output signal and generating a magnetic field sensor output signal.
The filter circuit
An anti-alias filter for producing an anti-aliased signal; And
A discrete time selective filter coupled to the anti-alias filter and sampling a signal representing the anti-aliased signal according to a sampling signal having a varying sampling frequency associated with the first varying modulation frequency filter),
And said discrete time selection filter has a changing notch frequency associated with said first varying modulation frequency. 13. The magnetic field sensor of claim 12, wherein the anti-alias filter has a corner frequency selected to reduce frequency components at least half of the maximum sampling frequency associated with the variable sampling frequency. 13. The magnetic field sensor of claim 12, wherein the variable sampling frequency is equal to integer times of the first variable modulation frequency. 13. The magnetic field sensor of claim 12, wherein the variable sampling frequency is equal to the first variable modulation frequency. 13. The magnetic field sensor of claim 12, wherein the variable sampling frequency is equal to twice the first variable modulation frequency. 13. The magnetic field sensor of claim 12 wherein the variable notch frequency is the same as the first variable modulation frequency. 13. The method of claim 12,
And a voltage controlled oscillator for generating a voltage controlled oscillator output signal having a varying frequency associated with said first varying modulation frequency. The method of claim 18,
And a clock generation circuit configured to receive the voltage controlled oscillator output signal and to generate at least one of the first modulated signal, the second modulated signal, or the sampling signal. The method of claim 18,
And a signal generation circuit for generating an output signal to control the variable frequency of the voltage controlled oscillator output signal. 21. The magnetic field sensor of claim 20, wherein the output signal of the signal generation circuit comprises a linear voltage signal that linearly-ramps from a minimum voltage value to a maximum voltage value. 21. The magnetic field sensor of claim 20, wherein the output signal of the signal generation circuit comprises a nonlinear voltage signal that varies from a minimum voltage value to a maximum voltage value. 21. The magnetic field sensor of claim 20, wherein the output signal of the signal generation circuit comprises a stepped voltage signal varying in the form of a plurality of discrete voltage steps from a minimum voltage value to a maximum voltage value. 21. The magnetic field sensor of claim 20, wherein the output signal of the signal generation circuit comprises a step voltage signal that varies in the form of a plurality of discrete voltage steps. The method of claim 1,
And a voltage controlled oscillator for generating a voltage controlled oscillator output signal having a variation frequency associated with said first variation modulation frequency.

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